This invention relates generally to apparatus and methods for the processing of cheese curd, and particularly wet cheese curd that is produced in the manufacture of cottage cheese.
In the manufacture of cottage cheese, the casein content of milk is coagulated as by introducing a starter, after which fermentation, with or without addition of acid, increases the acidity to the isoelectric point at which the casein is coagulated as a curd. Thereafter the curd is cut into small cubes and subjected to heating or cooking to arrest bacterial development. After cooling the curd is separated from the whey and subjected to one or more washings with fresh water. Various equipment and procedures have been used for draining and washing. In the older method, the material is cooked in a vat having a screened end whereby the whey is permitted to be drawn off. The curd may be subjected to one or more washings in the same vat, and the wash water likewise removed. A more modern procedure is to pump the material after heat treatment into a washer-cooler wherein the material is subjected to upwardly flowing wash water to displace whey from the curd fragments. Whey and the first wash water may be removed from the washer-cooler by decantation, and then the curd with the last wash water is pumped into a drainer-creamer. The drainer-creamer is a vessel having perforated vertical tubes extending upwardly from the bottom which allow water to drain out from the curd bed. While this type of equipment and method is an improvement over the older traditional methods, it has certain disadvantages. The curd tends to pack about the drain tubes, thus clogging the perforations, especially with soft curds. Also the time required to carry out effective drainage may be excessive, as for example 40 minutes to 2 hours. After the curd has been drained to about 20% solids content (oven dry basis) in such a drainer-creamer, the drain tubes are removed, and assuming that the curd is to be made into creamed cheese, a creaming mix is added and the mixture blended and pumped to the packaging line. Treatment within the drainer-creamer, including the addition of the creaming agent, is carried out in such a manner as to produce a desired solids content by weight, which in the case of cottage cheese is 20% solids. With such apparatus, the solids content of the curd varies from batch to batch. It will be evident that the production of a final product having a specified solids content of the curd after the draining operation described above often varies considerably from a predetermined target percentage.
Another type of draining apparatus which has been used to some extent is known by the trade name of "Curd-O-Matic". The Curd-O-Matic equipment makes use of a woven stainless steel belt upon which the curd is deposited, the belt being supported by a plurality of rolls and driven through washing and pressing stages. At the washing station the curd is subjected to sprays of refrigerated water, and in the pressing station the curd is pressed against the stainless steel belt and the underlying rolls by an overlying belt. The moisture content of the curd is adjusted by raising or lowering the overlying pressing belt. This equipment likewise has a number of disadvantages. Particularly, the size of the equipment is relatively large for a given capacity. The equipment is expensive because of its relatively complex mechanical construction. Also because of its complex construction the equipment is relatively unsanitary. Another equipment, similar to the Curd-O-Matic, has employed a screen belt made of plastic material supported by a table.
Another type of prior apparatus employs a drum having a perforated periphery that serves as a backing for a screen belt. The curd is delivered upon the screen and is pressed against the screen and drum by an overriding imperforate belt. Its performance likewise has been unsatisfactory due among other things to the relatively small area of drum perforations compared to the total area of the drum periphery.